Electrocatalysts are commonly used in PEM fuel cell electrodes to facilitate the oxidation of hydrogen gas at the anode and the reduction of oxygen gas at the cathode. These electrocatalysts commonly comprise nanosized platinum or platinum alloy catalyst particles supported on larger, high-surface area and electrically conductive carbon support particles. The purpose behind such a catalyst support structure is to optimize the amount of three-phase boundary reactive sites per unit area of the electrode so as to minimize catalyst loading requirements and to increase proton mobility through the fuel cell. Indeed, carbon has long been considered a most suitable catalyst support material because of its low cost, good electrical conductivity, high surface area, gas-diffusible friendly morphology, and chemical stability. An example of a specific carbon support material widely used for preparing fuel cell electrocatalysts is carbon black (Vulcan XC-72R).
Unfortunately, fuel cell performance setbacks that occur during vehicle cycling or extended operation, for example, are oftentimes partially attributed to the electrocatalytic oxidation of the carbon support material in the fuel cell's electrodes. This is so because any losses in carbon support material as a result of oxidation is accompanied by an associated loss in catalyst particles which, in turn, reduces the electrode's catalyst capacity. Attempts have thus been made to try and fabricate catalyst support materials that can withstand corrosive fuel cell environments and also provide comparable electrical conductivity and surface area characteristics to those of currently-used carbon materials. For example, TiO2-based materials are being actively investigated. But synthesis methods have not yet been developed that can produce these support materials such that they meet desired fuel cell operating criteria. Some common shortcomings of these current methods are that the synthesized TiO2 support material does not have enough open porosity and it is not easily formed into its more electrically conductive rutile crystalline phase. As a result existing TiO2 support materials display relatively low surface areas and pore volumes as well as high electrical resistivity values. It will be appreciated that the electrically conductive character of the TiO2 support materials is particularly significant for fuel cell applications. But the deficiencies of relatively low surface areas and pore volumes also render current TiO2 supports less desirable for the broad class of applications where support material electrical conductivity is not required.
Thus, a TiO2-based catalyst support material with an acceptable electrical conductivity and surface morphology, and a method for synthesizing the same, are needed.